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Definition df-xr 6821
Description: Define the set of extended reals that includes plus and minus infinity. Definition 12-3.1 of [Gleason] p. 173. (Contributed by NM, 13-Oct-2005.)
Assertion
Ref Expression
df-xr * = (ℝ ∪ {+∞, -∞})

Detailed syntax breakdown of Definition df-xr
StepHypRef Expression
1 cxr 6816 . 2 class *
2 cr 6670 . . 3 class
3 cpnf 6814 . . . 4 class +∞
4 cmnf 6815 . . . 4 class -∞
53, 4cpr 3368 . . 3 class {+∞, -∞}
62, 5cun 2909 . 2 class (ℝ ∪ {+∞, -∞})
71, 6wceq 1242 1 wff * = (ℝ ∪ {+∞, -∞})
Colors of variables: wff set class
This definition is referenced by:  ressxr  6826  ltrelxr  6837  pnfxr  8422  mnfxr  8424  elxr  8426  xrex  8486
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